n = int(input())
k = []
for b in range(n):
l = [[],[]]
m = int(input())
l[0] = list(map(int, input().split()))
l[1] = list(map(int, input().split()))
upl = []
downl = []
for i in range(m):
upl += [l[i%2][i]]
downl += [l[(i+1)%2][i]]
if m >= 2:
upl[1] += upl[0]
downl[1] += downl[0]
for i in range(2,m):
upl[i] += max(upl[i-1],downl[i-2])
downl[i] += max(downl[i-1],upl[i-2])
k += [max(downl[-1],upl[-1])]
for p in k:
print(p)